A three-dimensional model is a three-dimensional polygon representation of an object, and is generally displayed using a computer or another device. A displayed object may be an entity in the real world, or may be an imaginary object, and may have a size similar to that of an atom, or may have a quite large dimension. Any object that exists in the natural world may be represented by a three-dimensional model.
A three-dimensional model is usually generated using specialized three-dimension modeling tool software, or may be generated using another method. As data combining a point and other information, a three-dimensional model may be generated manually or may be generated according to a specific algorithm. Generally, a three-dimensional model exists in a computer or a computer file in a virtual manner. However, for a common user, sketching a two-dimensional line drawing on paper or on a screen to represent a three-dimensional object is closer to common people's habit of expressing a three-dimensional object and is a more convenient representation manner of a three-dimensional object or a three-dimensional model.
Three-dimensional models are widely applied. Actually, application of real three-dimensional models is earlier than application of personal computers. With popularization of personal computers, application of three-dimensional models that recur and are controlled using computers is widely spread to all walks of life and thousands of households.
Currently, three-dimensional models have been used in various fields. They are used to make exact models of organs in the medical industry, they are used in active characters and objects and realistic movies in the movie industry, they are used as resources in computer and video games in the video game industry, they are used as exact models of compounds in the field of science, they are used to present proposed buildings or scenery in the construction industry, and they are used in fields of designing new devices, means of transportation, and structures in the engineering field. In recent several decades, three-dimensional geologic models start to be constructed in the earth science field, and in near future, three-dimensional maps will also replace currently popular planar maps and become guiding tools necessary for common people to go out.
A conventional computer aided design (CAD) system can be used to create a three-dimensional object. A three-dimensional object may be exactly drawn in a three-dimensional modeling manner of CAD software. However, manpower is needed to participate in a whole process because of professionalism and complexity of this manner, which causes a quite heavy workload and is time-consuming. By comparison, two-dimensional line drawings are simple and easy to draw, and have long been used in people's most habitual expression manner of three-dimensional objects. However, an existing method for reconstructing a three-dimensional object using a line drawing cannot resolve a local optimum problem frequently occurring in a process of reconstructing a complex three-dimensional object. Therefore, algorithms cannot be applied in business application of reconstructing a complex three-dimensional object.